Steel alloys resistant to sulfuric acid and containing small quantity of alloying elements of copper,chromium,and tin or antimony



y 1969 HIROYUKI KUBOTA T L 3, 34

STEEL ALLOYS RESISTANT TO SULFURIC ACID AND CONTAINING SMALL QUANTITY OFALLOYING ELEMENTS OF COPPER. CHROMIUM. AND

we on ANTIMONY Filed April 5. 1966 I Sheet o! 6 I I I I I Solubilug I II I I I I l I I l l I 1 BY YUII rum, yoslno 130/10 rosmo Inna WM M 1%May 13, 1969 HIROYUKI KUBOTA ET AL STEEL ALLOYS RESISTANT 'ro SULFURICACID AND cou'ruumc SMALL QUANTITY OF ALLOYING ELEMENTS OF COPPER.CHROMIUM. AND TIN OR ANTIMONY Filed April 5, 1966 Sheet :2 0f 6 HIROYUKIKUBOTA ET AL May 13, 1969 3,443,934

STEEL ALLOYS RESISTANT TO SULFURIC .ACID AND comuuma SMALL QUANTITY OFALLOYING ELEMENTS OF COPPER. CHROMIUM. AND

TIN on ANTIMONY Filed April 5. 1966 Sheet ,3 of 6 B 05 \o S EM: w

7 50/. wo-c- 130C INVENTORj TOH-Ku MIN/4'0 1 WWW rsmzo d I Tvsma N66 0 Iwear 0 y 3, 1969 HIROYUKI KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT TO SULFURIC ACID AND CONTAINING SMALL QUANTITY OFALLOYING ELEMENTS OF COPPER, CHROMIUM. AND TIN OR ANTIMONY Filed April5, 1966 Sheet ore COMPARED MATERIALS A (Cu-Cr$b) COMPARED MATERIALS I(l-"" ""TA|NLEss) May 13, 1969 HIROYUKI KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT T0 SULFUR-1C ACID AND CONTAINING SMALL QUANTITYOF ALLOYING ELEMENTS OF COPPER, CHROMIUM. AND TIN 0R 'ANTIMONY FiledApril 5. 1966 Sheet 5 of 6 INVENTIONED STEEL F (cucr Ni sb-Sm May 13,1-969 UK KUBOTA ET AL 3,443,934

STEEL ALLOYS RESISTANT To suLFuRIc ACID AND CONTAINING SMALL QUANTITY OFALLOYING ELEMENTS OF COPPER, CHROMIUM. AND

TIN on ANTIMONY Filed April 5, 1966 Sheet 6 of 6 30c 50C 30C 149% 20% 9%THIS INVENTION PRIOR ART |ooc 50C 193 80% THIS INVENTION PRIOR ARTUnited rates 3,443,934 STEEL ALLOYS RESISTANT T SULFURIC ACID AND(JONTAINING SMALL QUANTITY OF AL- LOYING ELEMENTS OF COPPER, CHROMIUM,AND TEN 0R ANTIMONY Hiroynlri Kuhota, Tohru Mimino, Yuh Fukuda, YoslnoIshizu, and Toshio Nago, Kawasaki-ski, Kanagawa-lren, Japan, assignorsto Nippon Kokan Kabushikl Kalsha, Tokyo, Japan Filed Apr. 5, 1966, Ser.No. 540,343 Claims priority, application Japan, Apr. 12, 1965,iii/21,173; Aug. 27, 1965, til/52,245; Oct. 4, 1965, til/60,675

Int. Cl. C22c 39/26, 39/22 US. Cl. 75-125 8 Claims ABSTRACT OF THEDISCLOSURE A steel resistant to sulfuric acid consists essentially ofcarbon less than about .15 silicon less than about .40%, manganese in anamount less than about .50% phosphorus in an amount less than .03,sulfur in an amount less than about .03, copper in an amount of about.2.6%, chromium in amount 0.30.9% at least one substance selected fromthe group consisting of antimony and tin in an amount of about .050.5%and the balance iron.

This invention relates to steel alloys containing a relatively smallquantity of alloying elements and more particularly to steel alloyscontaining a small quantity of carbon, copper and chromium, whereinantimony or tin or both of them is incorporated in the steel alloys forthe purpose of greatly improving the corrosion resistance of the alloysagainst sulfuric acid.

Usual iron and steel materials which do not contain any special elementsand are not subjected to special surface treatments are readily corrodedby and dissolved in liquid sulfuric acid of a concentration of less than60%. With a concentration of more than 60%, corrosion proceeds violentlywhen the sulfuric acid is heated. Consequently, the usual life ofordinary iron and steel is very short when the same are used under suchcircumstances wherein they are contacted with sulfuric acid or with acorrosive gas which forms sulfuric acid upon condensation, and hence theloss of steel and iron due to such corrosion is very large. Whileconsiderable efforts have been made in the past regarding researches formetal materials which are resistant to the corrosive action of sulfuricacid, most materials which have been developed concern pure metals orsteels containing large quantities of expensive alloying elements andlow price steel alloy containing lesser amounts of alloying elements arenot yet readily and widely available. We have made exhaustive researchwith regard to the effect of Various elements upon corrosion resistanceof various types of steel against sulfuric acid or corrosive gasses ofthe same series and found low cost steel alloys containing lesserquantities of alloying elements and exhibiting extremely high resistanceagainst sulfuric acid under circumstances mentioned above.

More particularly, we have made many investigations for the purpose ofobtaining low price steel alloys which contain small quantities ofalloying elements and are suitable for use for such structures as steeltubes used in the low temperature sections of heavy oil burning boilers,for example, under circumstances containing or forming corrosivesulfuric acid. As is well known in the art, such elements as nickel,chromium, copper and the like are commonly recognized as suitableelements to impart resistance against sulfuric acid to steel alloys buttheir effect is very small and is not determinative. We have found thatby incorporating and causing to co-exist a suit- 3,443,934 Patented May13, 1969 f" I re able quantity of antimony, or tin, or both, in a basesteel material containing a small quantity of chromium, copper andcarbon, practical steel alloys which exhibit excellent corrosionresistant property under circumstances containing sulfuric acid orcorrosive gasses of the same series are provided. We have also foundthat the corrosion resistant property of this improved steel alloy canbe further increased by adding thereto a relatively small amount ofnickel, for example, from 0.30 to 0.80%. While the latter steel alloycontaining nickel has a considerable resistance against the corrosiveeffect of sulfuric acid, we have found that this steel alloy is alsosuitable for use as welding electrode or wire.

It is therefore the principal object of this invention to provideimproved steel alloys which contain a relatively small amount ofalloying elements and which have a high resistance to the corrosiveeifect of sulfuric acid.

Another object of this invention is to provide an improved weldingmaterial which can produce welded articles having high resistance tosulfuric acid.

According to one embodiment of this invention, the novel steel alloyconsists of less than 0.15 of carbon, less than 0.40% of silicon, lessthan 0.50% of manganese, less than 0.03% of phosphorus, less than 0.03%of sulfur from 0.2 to 0.6% of copper, from 0.3 to 0 .9% of chromium,from 0.05 to 0.5% of antimony or tin or both, and the balance of ironand impurities.

In the modified form, the novel alloy further contains from 0.30 to0.80% of nickel in addition to various ingredients mentioned above.

According to another feature of this invention, this last mentionedsteel alloy which contains nickel is utilized as welding electrodes orwelding wires.

A more complete understanding of our invention may be had from thefollowing description considered together with the accompanying drawingswherein:

FIG. 1 shows the manner of dissolving of ordinary steel in hot sulfuricacid;

FIG. 2 is a chart that shows the result of corrosion test in hotsulfuric acid made on the novel steel alloys containing lesserquantities of alloying elements and on control samples;

FIG. 3 shows the relation between piercing temperature and limitingreduction percentage;

FIG. 4 shows the test results of corrosion by hot sulfuric acid made onthe novel steel alloy and on contrast material;

FIG. 5 are photographs showing macro-structure of the contrast materialcaused by piercing test;

FIG. 6 are photographs showing macro-structures of the steel alloyaccording to this invention caused by piercing test and FIG. 7 arephotographs which show the results of comparison tests utilizing hotsulfuric acid made on welds prepared by the novel welding rod andconventional welding rod.

Referring now to the accompanying drawings, the manner of dissolving ofa common steel in hot sulfuric acid is generally shown by the solubilitycure shown in FIG. 1. Although this solubility curve varies in acomplicated manner as the conditions of the test are varied, it isconvenient to consider it by dividing it into four consecutive sectionsor regions I, II, III and IV. In accordance with this invention, inorder to decrease the resistances against corrosion in respectiveregions, there is proposed a basic steel alloy consisting of less than0.15% of carbon, less than 0.40% of silicon, less than 0.50% ofmanganese, less than 0.03% of phosphorus, less than 0.03% of sulfur,from 0.2 to 0.6% of copper, from 0.3 to 0.9% of chromium, from 0.05 to0.5% of antimony and the balance of iron and impurities, said basicsteel alloy being characterized by its low contents of alloying 3 4elements and high resistance against the corrosive effect corrosionresistance property of the steel alloy in the of sulfuric acid. Ifdesired, tin may be substituted for anregion IV shown in FIG. 1, Thecumulative effect timony in the above mentioned composition, in whichcaused by the coexistence of tin and antimony is more case the steelalloy consists of less than 0.40% of silicon, effective than theincorporation of either tin or antimony.

less than 0.50% of manganese, less than 0.03% of phos' 5 The reason forsetting the sum of tin and antimony in the phorus, less than 0.03% ofsulfur, from 0.2 to 0.6% of range of from 0.05 to 0.5% is that below thelower limit copper, from 03 to 0.9% of chromium, from 0.05 to of 0.05%it is diflicult to provide a satisfactory corrosion 0.5 of tin and thebalance of iron and impurities. Furresistant property while above theupper limit of 0.5

ther, in the two types of steel alloys just mentioned antithe hotworkability becomes poor.

mony or tin may be substituted by the same amount of As a result of manyexperiments we have found that the sum of antimony and tin. elementsthat impart a remarkable corrosion resistant With regards to respectiveelements utilized in the alloy property in regions I, II, III and IV,respectively, shown steels of this invention, carbon, when used inexcess of in FIG. 1 can be tabulated as shown in Table 1.

0.15%, not only deteriorates the anti-corrosion property but alsoresults in an undesirable increase in strength due to the co-existenceof other elements. Ranges of silicon and manganese of less than 0.4% andof les h 050%, TABLE 1.EFFECTIVE ADDITIVE ELEMENTS IN VARIOUSrespectively, are the ranges of deoxrdizlng agents re- REGIONS quired tobe used in the process of steel manufacturing. 1 n In W Upper limits of0.03% for prosphorus and 0.03% for sulfur represent the limits belowwhich it is difficult to Efiecfiveaddime918mm,, SB reduce the quantityof these elements in steel manufac- Sb Sn +Sn) turing art. Further,since phosphorus has a tendency of promoting corrosion, it is essentialto limit its upper range to the prescribed value. While copper is anelement effective to impart a corrosion resistant property,incorporation thereof of less than 0.2% is not effective and Table 2below Shows ypi l Chemical compositions of copper in excess of 0.6%results in difiiculties in the steel samples of steel alloys of thisinvention and those of conmanufacturing process. Chromium in the rangeof from trol samples and Table 3 shows the results of immersion 0.3 to0.9% exhibits a corrosion resistant property when tests in hot sulfuricacid.

TABLE 2.CHEMICAL COMPOSITIONS OF SAMPLES OF THIS INVENTION AND THOSE OFCONTRAST SAMPLES A B C D E F G H TABLE 3.THE RESULT OF IMMERSION TEST INHOT SULFURIC ACID MADE ON SAMPLE EMBODYING THIS INVENTION AND CONTROLSAMPLES Test condition, mg./cm. /5 h.

Sample 0.49%+30 C. 0.20%+30 C. %+50 C. %+60 C. %+75 C. 70%+100 C.80%+130 C. 90%+160 C.

0. 8 2. 2 2 43. 6 16. 8 8. 3 l2. 8 46. 1. 3 3. 2 11. 4 40. 8 19. 9 0. 914. 9 48. 0. 8 2. 7 15. 8 50. 7 16. 4 8. 0 18. 2 34. 1. l 2. 4-. 12. 548. 2 l6. 5 6. 6 10. 6 29. 0. 6 2. 7 21. 8 67. 2 17. 8 0. 6 15. 2 38. 2.3 13. 2 119. 0 239. 0 13. 2 7. 4 1.5. 5 54. 19. 5 15. 3 248. 0 380. 620. 6 8. 3 20. 4 65. 0. 04 2. 0 65. 7 229. 6 176. 2 I79. 6 208. 7 42.

it co-exists with copper, but chromium of less than 0.3% 60 In thesetables samples A to E inclusive represent the does not impart acorrosion resistant property. Further, novel steel alloys whereassamples F to H represent conchromium in excess of 09% causes poorworkability. As trol samples. FIG. 2 shows the test result shown inTable pointed out before, this invention is characterized by in- 3.

corporating tin or antimony or both for the purpose of Although steelalloys having compositions referred greatly improving the corrosionresistant property in reto above exhibit a high resistance against thecorrosive spective regions I, II, III and IV. Antimony content of effectof sulfuric acid it was found that the hot workmore than 0.5% lowers themelting point of the material ability and processability of steel alloyscontaining elethus imparing its hot workability, while antimony conmentswhich are effective to impart the corrosion resisttent of less than0.05% does not result in the increase in ance property at their upperlimits have lowered slightly the corrosion resistant property. The rangeof tin of from so that it is difiicult to produce products required tohave 0.05 to 0.5 is determined by the same reason as that accuratedimensions. We have endeavoured to develop for antimony. Thus a tincontent of above 0.5% greatly improved alloy steels containing lesserquantities of alimpairs the hot workability while a tin content of lessloying elements, having good resistance against corrosion than 0.05%does not contribute to increase the corrosion and being suitable forprecise hot working. The improved resistant property. Co-existence oftin and antimony in the steel alloy satisfying these requirementsconsists of less range of from 0.05 to 0.5% is intended for improvingthe than 0.15% of carbon, less than 0.40% of silicon, less than 0.50% ofmanganese, less than 0.3% of phosphorus, less than 0.03% of sulfur, from0.20 to 0.60% of copper, from 0.30 to 0.90% of chromium, from 0.30 to0.80% of nickel, from 0.05 to 0.50% of the sum of antimony and tin, andthe balance of iron and impurities.

The modified embodiment is characterized by containing from 0.30 to0.80% of nickel in addition to the various elements employed in thefirst embodiment. Incorporation of nickel in the range specifiedhereinabove 6 interfaces, thus forming cracks there and causing poor hotworkability. However, incorporation of Ni has an efiect of preventingeasy oxidation of iron. Further, Cu, Sb and Sn which are precipitatedand accumulated at the interfaces of grains will be mixed with nickeland form compounds of high melting points which contributes topreserving good hot workability.

Chemical compositions of typical samples of this embodiment and those ofcontrol samples are shown in the does not materially affect thecorrosion resistant property 10 following Table 4.

TABLE 4.-CHEMICAL COMPOSITIONS 0F TYPICAL SAMPLES OF THIS INVENTION ANDTHOSE OF CONTROL SAMPLES Chemical composition Samples C S1 Mn P S Cu CrNi Sb Sn A control 0.12 0.21 0.40 0.017 0.015 0.34 0.54 0.48 B thisinvention" 0.09 0.24 0.38 0.017 0.015 0.41 0.68 0.58 0.25 C thisinvention" 0. 11 0. 28 0. 35 0. 018 0. 015 0. 30 0. 48 0. 64 0. 42 Dcontrol 13 0. 30 0. 38 0. 020 0. 017 0. 42 0. 53 0. 0. 11 Ethlsinvention 0.13 0.31 0.42 0.019 0.014 0.41 0.53 0.54 0.17 0.12 F thisinvention 0. 09 0. 24 O. 46 0. 016 0. 015 0. 39 0. 52 0. 40 0. 0. 11 Gcontrol 0.13 0.19 0.45 0.012 0.015

H controL.-- 0.07 0.42 0.50 0.083 0.010

I control 0. 07 0. 55 0. 98 0. 036 0. 010

of the steel alloy. Nickel also prevents accumulation of additiveelements effective to impart the desired corrosion resistant property atinterfaces between crystalline particles which is caused by theselective oxidation of the iron component at the time of hot working. Inorder to impart satisfactory hot workability under severe operatingconditions it is necessary to select the lower limit of 0.30%, whereaswhen the upper limit of 0.80% is exceeded the corrosion resistantproperty of the steel alloys decreases gradually. This range of nickelis also suitable Each of these samples were immersed for 5 hours insulfuric acids of diiferent concentrations and maintained at differenttemperatures to test its corrosion, and the results are tabulated in thefollowing Table 5. As can be noted from this table samples of thisinvention, namely samples, B, C, E and F each containing nickel showedlesser corrosion than control samples. In Table 5, percentages show theconcentration of sulfuric acid, C. indicates the temperature of sulfuricacid and other numerical data represent corrosion expressed in term ofmg./cm. /5 hrs.

TABLE 5.IMMERSION TESTS BLADE ON SAMPLES OF THIS INVENTION AND CONTROLSAMPLES Test conditions Samples 0.49%, 30 C. 20%, 30 C. C. 50%, C. 60%,C. 70%, 100 C. 130 C. 160 C.

A control 0. 7 2. 1 17. 5 37. 5 13. 2 8. 2 12. 4 44. 7 B this invention-0. 6 1. 6 12. 1 33. 4 l5. 0 7. 4 13. 7 45. 4 0 this invention 1. 1 2. 419. 7 42. 2 14. 3 8.2 15.6 48.1 D con trol 0. 7 2. 8 16.0 40. 6 18. 4 7.0 14. 8 35. 9 E this invention 1. 0 3. 2 19. 1 50. 2 15. 6 6. 9 10. 332. 0 F this invention--- 0. 8 2. 4 l7. 2 48. 1 17. 0 9. 2 18. 0 37. 6 Gcontrol 2. 2 12. 6 19. 3 241. 2 13. 5 7. 0 14. 5 60. 2 H control..- 19.5 15. 3 248. 0 380. 6 20. 6 8. 3 20. 5 65, 2 I control 0. 04 2. 0 65. 76 176- 2 179. 6 208. 7 42. '7

for establishing adequate balance with regard to the ranges of otherelements incorporated.

Incorporation of a small amount of nickel prevents lowering in the hotworkability and processability of the steel alloy caused by the additionof elements which are effective to impart the desired corrosionresistant property so that it makes it possible to prepare various steelarticles including special steel plates, structural steels, steel tubeset cetera which are strictly required to have precise dimensions.Further, according to this modification, these products can be producedin mass production scale by similar procedures as usual hot workedproducts, thus reducing their cost of manufacture.

When elements such as Cu, Sb and Sn are incorporated according to thefirst embodiment, these elements will form a solid solution in ferriteand when the ferrous component oxidizes in preference to these elements,the concentration of solid solutions with Cu, Sb and Sn will increase,thus resulting in the precipitation and accumulation of these elementsat the interfaces of grains. It is presumed that this will causelowering of the melting point at these These results are plotted as aset of curves in FIG. 4.

With regard to more specific characteristics of steel alloys of thismodification, in order to determine the lim iting reduction percentage,we have adopted a method of working a test piece wherein the test piecewas put in a Mannessman piercing machine without utilizing a mandrel andthe ratio of the length of the test piece in which no crack was noted tothe total length of the test piece was determined as the limitingreduction percentage. With the roll gap of the Mannessman piercingmachine adjusted to 20 mm., a frustoconical test piece having a diameterof 25 mm., at one end, a diameter of 30 mm. at the opposite end, and alength of 150 mm., was put in the roll gap and worked. The limitingreduction percentage at the time when there was no crack was taken asand the limit of reduction percentage was calculated by expressing thequotient in percents obtained by deviding the difference between thetotal length of the test piece and the length of cracked portion withthe total length. By using this method, samples C and F embodying thisinvention and control samples A and I shown in 7 Table 4 were perforatedat 1150 C., 1200 C., respectively, to test their effectiveness withrespect to hot workability and the results of the tests are shown inTable 6 and FIG. 3 of the accompanying drawing.

TABLE 6.LIMITING REDUCTION PERCENTAGE These results clearly indicatethat incorporation of nickel to the first embodiment of this inventionwhich contains various elements including antimony eifective to impartcorrosion resistant property greatly improves the hot workability of theteel alloys.

Macro-structures of test pieces which have undergone the above test areshown by photographs in FIGS. 5 and 6 which clearly show excellentinternal characteristics of the steel alloys embodying this invention.The internal flexibility of each of the test pieces shown in FIGS. 5 and6 becomes lost as the temperature of the test piece is decreased, thusobscuring the interfaces between grains. This condition is moreprominent in the control sample shown in FIG. 5, especially so in 18-8stainless steel (FIG. 5B). The sample shown in FIG. 5, which containsantimony, shows fairly good internal characteristics at a temperature of1250 C., which is the appropriate temperature for piercing, but itslimiting reduction percentage was 50%. On the other hand, FIG. 6 showsthe internal characteristic of samples C and F which are incorporatedwith nickel in accordance with this invention. As can be noted from thisfigure internal characteristics as well as the limiting reductionpercentage have been greatly improved. (The limiting percentages being90 and 63%, respectively for samples C and F.)

As mentioned above, steel alloys according to the first embodiment ofthis invention are suitable for use as steel tubes or steel plates atlow temperature portions of boilers burning heavy oil wherein acircumstance in which corrosion by sulfuric acid prevails. According tothe second embodiment of this invention, a relatively low amount ofnickel is added to the composition of the first embodiment whereby hotworkability and processability of steel alloys are greatly improved,thus making it possible to prepare at lower cost such steel products asspecial steel plates, structural steel members, steel tubes and the likewhich are vigorously required to have precise dimensions. These productsfind their use in steam power plants, petroleum refining plants, citygas refining plants, synthetic chemical industry, and various chemicalplants for manufacturing ethylene, olefines and derivatives thereof.

We have also found that steel alloys containing nickel and preparedaccording to the second embodiment of this invention also suitable foruse as welding rod or wire for oxygen or acetylene gas welding. Suchwelding rod or wire can also be used in consumptive or non-consumptivewelding, such as TIG (tungsten inert gas) Welding. Corrosion of steel orsteel alloys due to sulfuric acid or an atmosphere containing corrosivegas which forms sulfuric acid is more severe at welds due mainly tometallurgical structure and construction thereof. In prior art, it hasbeen impossible to utilize weld rods or wires which form welds resistantto corrosive action of sulfuric acid.

Welding rods or Wires of this invention are especially suitable forwelding together mother metals having high resistance to corrosioncaused by sulfuric acid, such as those having compositions according tothe above described first and second embodiments, whereby the Weldedarticle will have homogeneous metallurgical structure. Thus, it becomespossible to make such welded products as steel plates, structuralsteels, steel tubes and the like. These products can be welded andtreated in the same manner as the case wherein ordinary welding rodsavailable on the market are utilized. As has been already pointed out,when elements such as Cu, Sb, Sn, et cetera are incorporated in steelalloys, these elements will form solid solutions in ferrite. However,when the alloys are heated to high temperatures it is expected thatferrous components will be oxidized in preference to these elements andCu, Sb and Sn will be precipitated and accumulated at interfaces betweengrains, thus decreasing the mechanical strength at these interfaces.However, nickel contained in the welding rods or wires of this inventionwill mix with Cu, Sb and Sn which are precipitated and accumulated atinterfaces between grains, thus increasing the melting point while stillmaintaining the Weldability at high values. Table 7 below illustrates apreferred composition of the welding rod according to this invention.

Table 7.Chemical composition of the welding rod In order to investigatethe ability and characteristics of the novel welding rod, two types ofwelding rods were prepared, i.e. one being a gas welding rod GA 43)having a tensile strength of more than 44 kg./mm. and an elongation ofmore than 20%) for mild steels prepared in accordance with JapaneseIndustrial Standards (JIS) Z 3201 and the other being the novel weldingrod, each having a diameter of 3.2 mm. Two sheets of 5 x 100 x 200 mm.steel plates having high resistance against sulfuric acid were preparedeach consisting of 0.08% of carbon, 0.19% of silicon, 0.47% ofmanganese, 0.012% of phosphorus, 0.013% of sulfur, 0.42% of copper,0.50% of chromium, 0.35% of nickel and 0.11% of antimony. These plateswere then butt welded with 60 V shaped groove provided at their centerby means of one pass manual welding procedure utilizing oxygen andacetylene gas test pieces of the dimensions of 3 x 20 x 40 mm. thusobtained was finished by machining, and tested their corrosion byimmersing them for 5 hours in sulfuric acids of various concentrationsand maintained at different temperatures. The result of the test isshown in Table 8 below and attached photographs denoted by FIG. 7. Thetable and photographs show that welds obtained by using the novelwelding rod have sufiicient corrosion resistance.

TABLE 8.-IMMERSION TEST OF THE WELDS Samples for immersion test 0.49%,30 C. 20%, 30 C. 40%, 50 C. 50%, 60 C. 60%, C. 70%, 100 C. 130 C. C

ii r%f?ii 'liilf 5. 2 2. e 9. s 18. 5 22. 0 s. 0 17. s 32t-"fiiiliiiliiffifflilf---. 1 4 6 11 13 15 18 20 Welds formed withconven- 5. R 2. 4 14. 8 47. 0 1R. 8 7. 8 l0. 0 31. 9 No ofphotogruphsshown in 5 U H w H m Remarks.In Table 8 percentages show the percentagesof sulfuric acids which are heated to respective temperatures designatedand the numerical data represent the quantity of corrosion in terms ofmg./cm. /5 hrs.

Generally, steel alloys of the type used herein exhibit a high value ofcorrosion at test conditions of about 40%, 50 C. and 50%, 60 C., so thatcorrosions under these conditions are most important. Conventional mildsteel generally shows values of corrosion of approximately from 100 to400 mg./cm. /5 hrs. under these test conditions, so that numerical datashown in the above Table 8 prove that the novel welding electrode hasmade a great advance in the Welding art.

It is to be understood that above described numerical data refer to theentire body of the test piece and that the data regarding weld only aregreater than the data shown in the Table 8.

While the invention has been described in connection with preferredembodiments thereof it should be understood that various changes may bemade therein without departing from the true spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. Sulfuric acid-resistant steel alloy consisting essentially of carbonin an amount less than about 0.15%, silicon in an amount less than about0.40%, manganese in an amount less than about 0.50%, phosphorus in anamount less than about 0.03%, sulfur in an amount less than about 0.03%,copper in an amount of about 0.2- 06%, chromium in an amount of about03-09%, at least one substance selected from the group consisting ofantimony and tin in an amount of about 0.05-0.5%, and the balance iron.

2. Alloy according to claim 1 wherein said substance is antimony alone.

3. Alloy according to claim 1 wherein said substance is tin alone.

4. Alloy according to claim 1 wherein said substance is a mixture ofantimony and tin.

5. Sulfuric acid-resistant steel alloy consisting essentially of carbonin an amount less than about 0.15%, silicon in an amount less than about0.40%, manganese in an amount less than about 0.50%, phosphorus in anamount less than about 0.03%, sulfur in an amount less than about 0.03%,copper in an amount of about 0.2- 06%, chromium in an amount of about03-09%, at least one substance selected from the group consisting ofantimony and tin in an amount of about 0.050.5%, nickel in an amount ofabout 0.3-0.80%, and the balance iron.

6. Elongated welding material formed of an alloy consisting essentiallyof carbon in an amount less than about 0.15%, silicon in an amount lessthan about 0.40%, manganese in an amount less than about 0.50%,phosphorus in an amount less than about 0.03%, sulfur in an amount lessthan about 0.03%, copper in an amount of about 02-06%, chromium in anamount of about 03-09%, at least one substance selected from the groupconsisting of antimony and tin in an amount of about 0.050.5%, nickel inan amount of about 0.3-0.80%, and the balance iron.

7. Elongated welding material according to claim 6 and wherein said ironincludes impurities.

8. Welding material according to claim 6 wherein said Welding materialis in the form of a wire.

References Cited UNITED STATES PATENTS 2,013,600 9/1935 Carius.

2,150,342 3/1939 Saklatwalla -425 2,867,531 1/1959 Holzwarth.

3,177,070 4/1965 Wacquez 75125 HYLAND BIZOT, Primary Examiner.

US. Cl. X.R.

